1. Field of the Invention
The present invention relates to architectural glass block panels and windows (“panels”) and methods of making such panels. More particularly, the invention relates to a new level of threat resistance achieved by these panels that far exceeds the current state-of-the-art in glass block systems with novel resistance to threats from forced entry, prisoner escape, fire arms, bomb blasts, and tornados.
2. Background of the Invention
Glass blocks are often employed instead of plate glass or other fenestration materials in the construction of walls and partitions. Aside from the aesthetic advantages that the glass blocks may provide over other glass materials, the glass blocks may be preferable to solid walls because they are transparent and allow light to filter through, thereby permitting viewing through the wall or creating a brighter room or office space.
Historically, most glass block installations are implemented using masonry. For small window applications, mortared panels are prefabricated, but overall size of the installation is limited due to the heavy weight and the potential for mortar to crack during transport and handling of the glass block panels. With the emergence of improved silicone sealants, larger glass block panels are now feasible and frames have been developed for partitions and windows. Such panels are sufficient for basic residential and commercial window applications, but far higher levels of performance are required to meet to the more stringent standards of threat resistance that are being established by government agencies.
To put the threat resistant performance requirements in context, commercial and residential windows require a cyclic air pressure tests that range from 35 pounds per square foot to 60 pounds per square foot. The Federal Emergency Management Administration (FEMA) tornado standards require windows to withstand air pressures of over 300 pounds per square foot. Government and military standards for blast resistance require resistance to pressures ranging from 576 pounds per square foot to over 1700 pounds per square foot. Commercial and residential glass block windows have no requirement for ballistic resistance, but Underwriters Laboratories (UL) has established a standard for jails and other secure buildings that requires the glass block to resist five shots from a 0.44 Magnum or three shots from a 30 caliber or 7.62 mm rifle. This far exceeds the capability of existing residential or commercial glass block panels or windows. Security installations like prisons require various levels of American Society for Testing and Materials (ASTM) standard forced entry (or escape) resistance which may include dozens of hits by hammers, chisels, sledge hammers and battering rams as well as attacks using ripping bars, fire extinguishers and propane torches. Previous state-of-the art glass block panels or windows intended for residential and commercial window applications are not designed for those types of assaults and cannot even begin to resist such challenges.
The present invention addresses these long-standing problems in the industry by disclosing an improved glass block window system that achieves threat resistance much greater than the prior art. Unlike relatively flimsy frames used in residential and commercial windows, the framework provided herein is a very strong and rigid unitized structure made of steel or other rigid material that is designed to resist very large cyclic and impulsive pressure forces as well as powerful localized point impacts. Unlike the traditional hollow glass blocks, the glass blocks used in the threat resistant structure are solid laminated glass blocks (U.S. application Ser. No. 12/732,727, which is hereby incorporated by reference) specially designed to withstand very high impact from both blunt and sharp instruments and projectiles. The sealant used to hold the glass blocks (e.g., modified urethane) is formulated for very high performance flat glass configurations. These characteristics along with other aspects of the present innovative design result in a very high-performance glass block window system possessing a dramatically improved threat resistance.